Growth hormone is a polypeptide hormone synthesized in and secreted by the adenohypophysis (anterior lobe of the pituitary). Growth hormone is synthesized as a precursor protein (pre-growth hormone) containing an N-terminal signal peptide and the growth hormone sequence. The amino acid sequence for bovine growth hormone has been determined (Dayhoff, M. D., et al, Atlas of Protein Sequence and Structure, Vol. 5, Supp. 3, pp. 345-352, National Biomedical Research Foundation, Washington, D.C. (1978).
Growth hormone is normally produced throughout life, although in highest amounts during the pre-adult period. The hormone is required for pre-adult growth. Although its mechanism is not understood in detail, growth hormone is known to promote skeletal growth, nitrogen retention, protein synthesis and affects glucose and lipid metabolism. In other words, growth hormone is a general anabolic agent.
Uses of bovine growth hormone are based on its known biological activity described above. Bovine growth hormone may be administered to young cattle in order to increase their rate of growth and weight gain, thereby decreasing the time required between birth and marketing for beef. The resulting increase in meat production could be significant. Furthermore, bovine growth hormone differs from ovine growth hormone by only a few amino acids. Thus, bovine growth hormone may be administered to sheep to accomplish the same goal in sheep as in cattle, i.e., increasing rate of growth and weight gain and thus increasing meat production. It is also possible that bovine growth hormone can be administered to hogs or other animals to accomplish the same goals.
Basic techniques for cloning DNA sequences are now known. For example, Seeburg, P. H., et al, Nature, 270, 486 (19771 describes the cloning of the rat growth hormone gene; Shine, J., et al, Nature, 270, 494 (1977) describes the cloning of the human chorionic somatomammotropin gene; and Derynck, R., et al, Nature, 285, 542 (1980) describes the cloning of the human fibroblast interferon gene.
Methods for the expression of heterologous DNA in a microorganism are now known. In principle, the heterologous DNA coding sequence is inserted in a DNA transfer vector at a point located within an expressible operon. For the production of a hybrid protein the inserted sequence must be in reading frame phase with the coding sequence of the operon, and oriented in the same direction with respect to translation. When the conditions are met, translation of the operon results in xe2x80x9creadthroughxe2x80x9d to the inserted coding sequence such that the protein produced is a fusion protein comprising an N-terminal amino acid sequence coded by the expressible operon, followed by an amino acid sequence coded by the insert. See Polisky, B., et al, Proc.Nat.Acad.Sci.USA, 73, 3900 (1976); Itakura, K., et al, Science, 198, 1056 (1979). Several expressible operons have been employed, including those for xcex2-galactosidase, xcex2-lactamase, and tryptophan.
Abbreviations used herein are those abbreviations commonly accepted and used by one of ordinary skill in the art.
For example, these abbreviations are accepted by the J.Biol. Chem., without further elucidation,
The present invention discloses the cloning of a DNA coding for bovine growth hormone and the expression of the cloned DNA in microorganisms.
mRNA coding for bovine growth hormone is isolated from bovine pituitaries, A reverse transcript (a cDNA copy) of the mRNA is prepared and inserted into a transfer vector, The transfer vector is used to transform bacteria which express the cloned cDNA.